The present disclosure relates generally to the field of micromachining techniques, and more particularly relates to a method for bulk forming through-wafer vias with a wet etchant.
Wet etching of silicon wafers with potassium hydroxide (KOH) is a well-known bulk micromachining technique. Wet etching as a micromachining technique provides a lower cost of manufacturing, since the etching can be done in batch processes and there is no need for expensive etching equipment, such as plasma etchers. The use of KOH for etching silicon wafers produces smooth side walls. KOH etching of <100> silicon wafers produces pyramidal shapes, i.e., the side walls of the vias are not parallel but instead incline relative to each other. The pyramidally-shaped openings through wafers have an enlarged footprint, thus lowering the upper limit of the number of openings that can be produced in the wafers and lowering the density of vias capable of being etched in a given footprint.